The present invention relates to data communications equipment, e.g., modems, and, more particularly, to the setting of communications parameters within the data communications equipment.
Today, more and more companies are allowing employees to work from home, i.e., to "telecommute." To facilitate the ability of employees to work at home, some companies provide their telecommuting employees with personal computers. The latter assist the telecommuting employee in performing their work at home as if physically at the office. For example, an employee may be able to just as easily write a report using a word processor on their personal computer at home as compared to performing the same activity at the office. As a result, the personal computer provides a degree of independence from the workplace. However, during a work day the telecommuting employee may still have the need to occasionally access additional computer resources located at the company's facilities. The telecommuting employee may make a number of such data connections during the course of a day for very short time periods to obtain a copy of a file, exchange electronic mail, reconcile databases, etc.
Any computer facility is typically accessed by the telecommuting employee via a switched data connection through the public switched telephone network (PSTN). In order to establish a switched data connection, the personal computer of the telecommuting employee includes data communications equipment, e.g., a modem, that is coupled to the PSTN. Generally, the telecommuting employee simply enters a command into the personal computer to instruct the modem to dial a telephone number associated with the computer facility. After dialing and detecting an answer tone from a far-end modem of the computer facility, both the local modem and the far-end modem perform a "hand-shaking" procedure to establish the data connection.
This "hand-shaking" procedure is performed by both modems every time a data connection is established between the telecommuting employee's home and the computer facility. As part of this "hand-shaking," or initialization, procedure, each modem performs a "training process" in which each modem evaluates the analog communications channel across which the data connection is established. This evaluation is performed so that each modem can process a received signal to correctly recover the transmitted information from the far-end. For example, each modem typically includes an equalizer to correct for "inter-symbol interference" (ISI). In order to correct for ISI, a predefined test signal is transmitted between the modems during the above-mentioned training process. Each modem evaluates the received test signal and calculates a set of parameters referred to as "tap values" for the respective equalizer.
Unfortunately, the higher the data communications speed, the longer this training interval. In particular, high-speed data modems have the characteristic of taking a significant amount of time, e.g., 10-20 seconds, to establish a data connection. Further, it is likely that in a telecommuting environment high-speed data connections will be established between a telecommuting employee and their company's computer facilities for short periods of time throughout the course of the day. This is simply because the high-speed transfer of data, i.e., information, increases productivity, and because some pc-based applications, like image transfers, require a large amount of data. Consequently, this 10-20 second training delay becomes an annoyance in a telecommuting environment. In addition, the longer it takes to establish a data connection, the more time that a particular modem of the computer facility is busy--which increases the likelihood of other telecommuting employees receiving a busy signal when they attempt to make a data connection to the computer facility of the company.
While some "fast-training" mechanisms exist in the prior art, these prior art solutions are not the complete answers in a telecommuting environment. For example, in private line networks there is a dedicated facility between each endpoint of a data connection. In such a situation, the same facility is always used so that configuration parameters, like equalizer tap values, need, generally, only be calculated once. Once calculated, these configuration parameters are stored for latter recall by each modem within each endpoint. However, in the telecommuting environment--there are no dedicated facilities--only switched facilities between each endpoint of the data connection. Similarly, in the co-pending, commonly assigned, patent application of Ken Ko entitled "Independently Switched Voice and Data Calls Using a Simultaneous Voice and Data Modem," Ser. No. 08/216,373, filed on Mar. 23, 1994, the local loop between a user and their central office is terminated between two modems--one modem within the user's home and one modem within the central office of the user. In this environment, the parameters of the dedicated local loop are measured and stored for future reference in these two modems. In fact, the central office of the user stores configuration parameters, like tap values, based upon the telephone number associated with the respective local loop. However, again, in the typical telecommuting environment--the local loop is not isolated between two modems--instead the communications path between the two data endpoints include switched facilities.